1. Field of the Invention
The present invention relates to an electromagnetic controlled fuel injection apparatus applied to an electromagnetic controlled unit injector, etc. for a diesel engine. Fuel injection timing thereof is controlled by means of a poppet valve which is reciprocated by means of a solenoid device to open or close a passage between a fuel passage to a plunger chamber where fuel is received and compressed to high pressure and a spill passage to a fuel return line.
2. Description of the Related Art
An electromagnetic controlled unit injector applied to a diesel engine is composed such that fuel injection timing is controlled through shutting-off or allowing communication of a fuel passage, which connects to a plunger room where fuel is introduced and compressed to high pressure, with a spill passage connecting to a fuel return line by closing and opening a poppet valve reciprocated by a solenoid device and a poppet valve spring.
Injection of fuel begins when the poppet valve sits on the seat portion of the valve seat and ends when the poppet valve leaves the seat portion. There is a problem that, a bounce of the poppet valve occurs when the poppet valve seats on the seat portion of the valve seat or when the poppet valve seats on the bottom seat face of the injector body. That is, the poppet valve rebounds from the seat portion at the beginning of injection and rebounds from the bottom seat face of the injector body at the end of injection, which causes irregular fuel injection at the start and end of injection.
A means to prevent the occurrence of valve bounce is disclosed in JP5-223031A (U.S. Pat. No. 5,284,302).
According to this disclosure, in an electromagnetic fuel injection valve, a magnetic powder of a specified mass is received in a sealed inside space formed inside the needle valve so as to be axially movable therein. The magnetic powder, which is an inertial collision element, moves in the inside space by inertia force generated by the movement of the needle valve and collides against the undersurface of a plug screwed in the upper part of the inside space of the needle valve or against the bottom face of the inside space. The occurrence of bounce of the needle valve when the needle valve seats on the stopper plate in the upper part or on the valve seat portion in the lower part is restrained, and the durability of the electromagnetic fuel injection valve is improved.
However, in JP5-223031A (U.S. Pat. No. 5,284,302), the magnetic powder is received in an enclosed space inside the needle valve. The magnetic powder is allowed to move in the enclosed space by the inertia force to collide against the undersurface of a plug screwed in the upper part of the inside space of the needle valve. There is a fear that the magnetic powder leaks out of the inside space when enclosing it in the inside space or the magnetic powder leaks through the gap in the screwed part of the screw plug and mixes in the fuel, resulting in jeopardizing safe and stable operation of the engine.
Further, when a magnetic substance is used for the valve body of the electromagnetic valve, the original magnetic flux is disturbed, attraction may change, and it may happen that the magnetic substance does not contact the bolt when bouncing if the magnetic substance is attracted by the magnetic force of the solenoid. When the magnetic substance rebounds, it does not collide with the bolt, and a bounce restraining effect does not result.
When a nonmagnetic solid substance is used, influences by magnetic force do not occur when it is used as an electromagnetic valve. However, in order to allow it to collide with the needle valve with a specified time lag, matching of the distance of movement, orifice diameter, spring force of the spring, and mass of the piston is necessary. As to the movement of the needle valve, there may be a case where the direction of the movement of the needle valve changes halfway from the opening direction to the closing direction, or vice versa, and the needle valve moves between the seat position and midway of its lift when bouncing repeats, so there is a possibility that the distance of movement of the inertial collision element changes.
Further, it is expected that the bounce is restrained by a single collision of the inertial collision element such as the magnetic powder, and to cope with a repetition of bounce is not considered.
Particularly, it is effective to inject fuel in amounts to meet exhaust emission regulations, and when the electromagnetic valve is energized again immediately after the first injection in multistage injection, the position of the inertial collision element in the inside space of the needle valve varies according to the conditions.